Drier for granular plastic



Oct. 26,1948. R. R. LEISKE 2,452,249

DRIER FOR GBJANULAR PLASTIC Filed March 4, 1946 INVEN O "I A W Patented Oct. 26, 1948 UNITED STATES PATENT OFFICE 2,452,249 DRIER FOR GRANULAR PLASTIC Roy R. Leiske, Milwaukee, Wis. Application March 4, 1946, Serial No. 651,864 2 Claims. (Cl. 34-183) The present invention relates generally to improvements in the art of manufacturing diverse articles from plastics, and cally to improvements in the construction and operation of mechanism for conditioning materials such as granular or powdered plastic stock.

The primary object of my present invention is to provide an improved unit for effecting automatic and thorough mixing, drying and preheating of a constantly advancing stream of granular or powdered material, and especially plastic stock, as it travels from a supply source toward a molding machine for the finished plastic articles.

In the art of molding plastic articles it is necessary in order to insure rapid production of successive perfect specimens, that excessive moisture be removed from the plastic stock before it is admitted to the final molding machine. This granular or powdered plastic stock is ordinarily supplied in bulk with relatively large batches thereof confined in open containers, and is susceptible of absorbing and confining considerable moisture which, if admitted to the molding machines, necessitates prolonged curing time and thus materially delays production. The excess moisture should therefore be removed and should preferably be eliminated just prior to the introduction of the stock material to the molding apparatus. In' order to avoid loss of time and to enhance production as much as possible, it is also desirable to preheat as well as to dry the stock material and to deliver the preheated dry granular plastic material in the form of a continuous rapidly advancing stream directly into the receiving hopper of the molding device, and

so far as known, no mechanism foraccomplishing these desirable results has heretofore been commercially developed and marketed.

It is therefore a more specific objectvof the present invention to provide improved mechanism for converting successive batches of granular of powdered plastic stock into a rapidly-progressing stream, and for effectively removing excess moisture from the advancing mass of material while also preheating the material without danger of scorching it.

Another specific object of this invention is to provide a simple and compact granular or powdered material drying unit especially adapted to treat plastic stock, which may be readily applied to or operatively associated with the inlets of various types of plastic article molding machines.

A further specific object of my invention is to provide an improved granular or powdered material feeding, agitating, preheating and drying assemblage which will not clog. and wherein all moving. parts are driven by a common motor through simple driving mechanism which is readily adjustable to vary the operating characteristics of the assemblage.

Still another specific object of the invention is to provide an improved continuous dryer and prethe like, which is durable in construction, and which may also'be manufactured and operated at moderate cost.

An additional specific object of the present invention is to provide an eflicient drying and preheating unit for granular or powdered material, which is continuous and automatic in action, and in which the excess moisture is rapidly and effectively removed while possible scorching is positively prevented.

These and other specific objects and advantages of the present invention will be apparent from the following detailed description.

A clear conception of the features constituting my present improvement, and of the mode of constructing and operating dryer and preheating units embodying the invention, may be had by referring to the drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

Fig. 1 is a side elevation of one of my improved continuous granular or powdered material treating units;

Fig. 2 is a central longitudinal vertical section through the unit of Fig. 1;

Fig. 3 is a part sectional end view of the same unit, looking toward the inlet end thereof;

Fig. 4 is a transverse vertical section through the preheating and drying zone of the unit, taken along the line l-i of Fig. 2; and

Fig. 5 is a fragmentary longitudinal vertical section through a modified type of preheating and drying assemblage.

While the invention has been shown and described herein as being especially applicable to electrically driven and heated units for continuously agitating, preheating and drying granular or powdered materials for producing plastic articles, it is not my desire or intention to unnecessarily restrict the utility of the improvements by virtue of this limited disclosure.

Referring particularily to Figs. 1 to 4, inclusive, of the drawing,the improved material treating unit shown therein comprises in general a main housing or casing l forming an elongated approximately horizontal trough a having an inlet hopper or supply opening 9 at one end and a nism for readily agitator shaft 22 may material discharge opening or outlet II at its opposite end; a rotary agitating and conveying screw Ii mounted upon a main shaft i2 and being cooperable with the bottom of the trough 8 to constantly stir and advance granular or powdered material along the casing 1 from the inlet 9 to the outlet It; means such as a thermostatically controlled electric heater I! for heating the portion or zone of the trough 2 between the material inlet and outlet; a suction device or blower it having an inlet conduct i6 communicating with the heating zone ll through a hood I! and a series of heme openings it formed in the top enclosure I! of this zone, for constantly removing vapor from within the heating zone; a mixing and bridge preventing rotor 20 mounted in the inlet opening S of the casing l; common means such as an electric motor 2! for simultaneously rotating the conveyor screw it and rotor-20 and for driving the exhaust blower i; and mechavarying the speed of operation of the conveyor II and mixing rotor 20.

The main casing 1, motor 2|, and the transmission mechanism, may be mounted upon a common base 22 so as to provide a single unitary assemblage adapted to be mounted as a unit upon various types of plastic article molding machines, and the casing I may be formed of sheet metal or other suitable material. The hopper 9 is preferably provided with a series of transverse bars 23 located above the rotor 20, for supporting successive containers or receptacles for granular or powdered stock, in inverted position upon the treating unit; and the revolving rotor comprises an annular series of rods mounted upon a shaft 24 and is operable to prevent bridging of the gravitating stock across the inlet opening and to agitate and loosen the entering stock. The shafts 2!, i2 may be -journalled for rotation in the casing 'l in any convenient manner, and the be driven from the conveyor shaft i2 through a V-belt drive 25, or otherwise. S

The portion of the rotary conveyor H disposed beneath the inlet opening 9, 'may be formed as a 7 continuous helical flight. but the portion of this conveyor which is located within the heating zone ll. preferably consists of a series of segregated flights 28 which cooperate to form a mutilated helix or screw adapted to thoroughly mix and agitate the material as it advances toward the outlet opening ll. The heater I2 may be of a conventional electric typethermostatically controlled so as'to limit the degree or heating, and this heater is should be externally insulated as shown, so as to transfer heat only through the trough Hate the heating zone ll. The end wall of the casing I'nearest the outlet I0, is provided with an airj-inlet filter 21, and the openings It in the top plate I! of the heating and agitating zone 14 are preferably provided with bailles 28 inclined as shown, in order to cause the vapor removing air to most efiectively circulate throughout the zone 14. The suction blower liwhich has its intake conduit Ii connected with the openlugs 18 through the hood ll. may be of any suitable ty-pe direct connected to the driving motor 21, and has a discharge or outlet opening 29; and the intake conduit ll should be sumciently flexible to permlt'adiustment of the motor 2| as hereinafter described.

It is desirablein orde to insure most eilicient agitating, pre-heating and drying of the material treated by the unit, to beable to vary the speed of rotation of-the conveyor It so as to positively prevents bridgin of 1 operable at much should also be set to hopper Q. The

lengthen or shorten the time of treatment, and such variation in time may be readily effected by utilizing driving mechanism such as shown in the drawing. Since the motor 2| is ordinarily higher speed than is desired at the conveyor II, it is also desirable to provide speed reduction means for the conveyor driving shaft l2, and in the improved unit, the mechanism for varying and reducing the speed of rotation of the conveyor Ii is interposed between the motor 21 and the main shaft l2.

A countershaft so is iournalled for rotation in a gear casing 3| mounted upon the base plate 22, and has a unitary or one-piece sheave 32 provided with a peripheral V-shaped groove, secured to its outer end; The motor shaft. 32 is provided with a two section sheave t4, the sections of which cooperate and are urged toward each other to provide a V-groove of variable width, and a resilient endless V-belt 25 coacts with the alined grooves of the two sheaves 22, 34. The motor 2| is slidably mounted upon an 38 secured to the base 22, ward and away from the base 22 by means of a screw 21 and a hand wheel 28, so that the belt 35 may be caused to forcibly separate the sections of the driving sheave flmore or less and to ride ofv this sheave diilerent disdriven sheave 22 and shaft 20. This type of variable speed mechanism is well known to the trade, and may be utilized to vary the speed of rotation of the conveyors ll, 26 throughout .a considerable range.

The speed reducing gearing which is housed within gear casing 2 l may be of any suitable type, and as shown, this gearing comprises a helical toothed pinion 29 secured to the countershaft 30 and meshing with a helical gear 40 secured to a second countershaft ll journalled in the casing 2i; and a worm 22 secured to the shaft ll and drivingly coacting with a worm wheel 42 secured to the conveyor shaft i2, see Fig. 2. This gearing will obviously cause the conveyors ll, 28 to be driven at a much lower speed than that of the motor 2 l', but any changes in speed eifected by the speed varying mechanism will cause the rotary conveyors to operate slower or faster as so as to insure most efl'ective drying and preheating of the material being treated without scorching or melting the same.

' During normal operation of the improved mixin, drying and'pre-heating unit, may be operated to constantly revolve the rotor 20 and conveyors ii, .28 at the desired speed, and to simultaneously actuate the suction blower ll so as to cause atmospheric air to be drawn into the heating one it past the filter 21 and through the opening i l,- and to be discharged around the -bailles 28 and through the openings l8. hood and conduit l2 to'the blower. The heater l2 insure proper heating but to avoid overheating, by adiusting its thermostatic control it in a well known manner, whereupon successive open topped receptacles containing batches of the granular or powdered material which is to be treated, may be inverted and applied to the supporting bars 23 within the supply material then drops by gravity into the trough I and into the path of the revolving initial conveyor screw it, while the rotor 22 initially stirs or agitates the descending mass and the material across the hopper outlet.

desired,

the motor 2| The initial conveyor screw H thoroughly mixes other purposes, and the improved device may be and agitates the granular or powdered substances manufactured and operated at moderate cost which are deposited in its path, and gradually but and functions automatically after proper adjustcontinuously advances the material along the ments have been made. trough 8 and into the heating zone I 4. Here the 5 It should beunderstood that it is not desired mutilated conveyor or vanes 28 continue the agito limit this invention to the exact details of terial are stirred and subjectedto heat from the tions within the scope of the appended claims heater I3, moisture is driven from the massand may occur to persons skilled in the art.

rises in the form of vapor into the zone It. When I claim:

the material enters the heating zone 14, the In a drying unit f r granular st a asgreater percentage of the moisture is promptly ins having an upwardly open trough Section and removed in the initial part oi this zone, and rea ho n lly al ned enclosed ro h Section sidual moisture is thereafter removed as the i5 separated from the opensection by a partition oughly dried and pre-heated product is eventually at its end remote from said partition, horizont lly delivered in the form of a continuous stream, alined screw conveyors coacting with the bottoms sufllcient to melt the same, but the pre-heating ly mall i me r and pi ch n th nv or necessary for final melting. interrupted helical flight 01 larger diameter and While the revolving segregated conveyor vanes greater Ditch, an agitator rotatable Within Said 26 of Figs. 1 and will operate satisfactorily, other inlet ve s d small r conveyor, a suct on detypes of rotary conveyors may be utilized to trans- 30 Vice for ith wing v por upw ly f m With- One such modified conveyor i shown in Fi 5, means for actuating said conveyors and said agiwherein the mutilated conveyor screw or succesand Said devicesion of flights 26',is carried byadrum 44 mounted In a drying unit for granular P therethrough, and if o d ir d, some of the nrected open inlet extending throughout its length such a modified final conveyor assemblage, the 45 sides of said partmonthe conveyor vapors re ulti from heath, Wm be 5 flight of larger diameter and greater pitch, an ith from within thegdrum 23533 31: agitator rotatable within said inlet above said scribed, conveyors and said agitator and said device, and F the f r g i detailed description it means for heating said enclosed trough section.

shoujlg be apparent that my present invention ROY LEISKE- prov es an improved unit for automatically stirring. drying and pre-heatlng a continuous stream REFERENCES CITED of granular or powdered material in a most em- 33 references are of record m the cient manner. The improved unit is obviously e o s iSlislrl'lple findbcliontipact in construction, and is read- UNITED STATES PATENTS app ca e 0 various types of plastic mold Numb r ing machines. and the several parts of the mech- 536285 Gri iu ADI' a$61895 aIllSm may be quickly and conveniently adiusted 640,628 Bussells I m Jan 2' 1900 so as to insure desired operation without danger 1,023,157 Laieuille n Apr 1 1912 of over-heating the product. The rotor 20 eflec- 1,126,587 Suzuki Jan 26 1915 tively prevents clogging due to the admission of 1,190,127 Disdier Ill :1 Jul' '4' 1916 large masses of granular or powdered material 1,301,409 DuPont Apr 22 1919 the particles of which have lumped together, and 1,421,283 Meakin aune'zv' 1922 the pro-heating oi the final product greatly facili- 1,704,413 Wait Mar 5' 1929 tates its final use in a molding machine. While 1,795,302 Forrest Mar '10 1931 the improved assemblage is especially adaptable 1.988.678 Arnold Jan 22' 1935 for handling granular or powdered plastic stock, 2,295,918 Thomas Sent 15 1942 the unit may also be used advantageously for 2,334,015 Levine et a1 Nov. 9, 1943 

